Acetabular cups are well known as a component of prosthetic hips. The cup is inserted in the acetabulum in a prepared cavity and normally fixed in place by a cement mantle.
Loosening of the cup in the cement mantle and subsequent undesirable rotation of the cup in the mantle has long been a problem. Various techniques have been tried in the past to avoid this problem. For example, roughening of the outer surface of the cup to improve adhesion of the cement, the use of spacers to help form a cement mantle of uniform thickness, wire screens which are embedded in both the cement and the cup surface, patches of frit adhered to the cup's outer surface and angular protrusions to resist rotation have all been used with some degree of success.
The use of spacers or studs which are made of a material which is chemically compatible with the cement mantle is known. Coating of the outer surface of the cup with a material which is chemically compatible with the cement is also known. Cement-receiving grooves in the outer surface of the cup and in protrusions on the outer surface of the cup are also known and used.
However, breakdown of the cement mantel and a corresponding loosening of the acetabular cup in the mantel remains a problem. The problem causes pain and discomfort for patients in which the prosthetic acetabular cup has been installed. An installed hip in which the acetabular cup has come lose and rotates must normally be revised, requiring the patient to undergo further surgery.
A cup structure for use in cement fixation which will further reduce breakdown of the cement mantel and avoid the resulting rotation of the cup in the mantle is desirable.